/*
 * @lc app=leetcode.cn id=617 lang=cpp
 *
 * [617] 合并二叉树
 */

// @lc code=start
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution
{
public:
  TreeNode* mergeTrees(TreeNode* root1, TreeNode* root2)
  {
    if (root1 && root2) {
      root1->val = root1->val + root2->val;
      root1->left = mergeTrees(root1->left, root2->left);
      root1->right = mergeTrees(root1->right, root2->right);
      return root1;
    }
    return root1 ? root1 : root2;
  }
};
// @lc code=end
